<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style type="text/css">
    * {
        list-style: none;
        padding: 0;
    }
        span{
            padding: 12px 12px;
            background: url("img/icon3.png") no-repeat;
            font-size: 0px;
            /* 相对定位居中 */
            position: relative;
            top: -6px;
            /* 设置margin会影响兄弟元素 */
            margin-right: 10px;
        }
    </style>
</head>
<body>
    <ul>
        <li><span></span>标题</li>
    </ul>
</body>
</html>